Canoscan D1250U2F is not supported in Windows 7, and they have no plans to make a driver.
Below is the answer I got

Dear Kristian Nielsen:

Thank you for your inquiry. We value you as a Canon customer and
appreciate the opportunity to assist you with your CanoScan D1250U2F.

Unfortunately, the CanoScan D1250U2F is not compatible with the Windows
7 Operating System. We apologize for this inconvenience. Because your
scanner is not compatible, you qualify for the Canon Loyalty Program.

Canon’s Loyalty Program is for out of warranty units which have been
diagnosed to require service, or for some reason are incompatible with a
new or upgraded system. This option allows you a one-time opportunity
to purchase a new product of the same type, discounted from the list
price.

I just read somewhere that it is only the installer that doesn’t work on windows 7 and it is possible to extract the files with a zip utility like 7zip and then manually install them. Now I can’t find the article or posting anymore but I am going to try my best.

P.s. download from a reliable site to avoid viruses if you are downloading a zip utility.